Magnet pole indicators



Nov. 27, 1956 H. MOHR MAGNET POLE INDICATORS Filed Sept. 21, 1953 Fig. 7

United States Patent MAGNET POLE INDICATORS Heinrich Mohr,Dortmund-Aplerbeck, Germany, assignor to Deutsche EdelstahlwerkeAktiengesellschaft, Krefeld, Germany Application September 21, 1953,Serial No. 381,373 Claims priority, application Germany September 23,1952 Claims. (Cl. 324-34) The invention relates to a magnet poleindicator by means of which the north and south poles of permanentmagnets, electromagnets and direct-current coils of all kinds can bereliably, rapidly and simply ascertained.

Hitherto, pole indicator instruments have been proposed which are likecompass needles and have the disadvantage that the magnetism soonbecomes weakened or disappears entirely during use. Moreover, some skillis required to apply the instrument to the article to be tested if asatisfactory indication is to be obtained.

The magnet pole indicator according to the invention obviates or lessensthese disadvantages. A form of construction of the magnet pole indicatoraccording to the invention is shown by way of example in theaccompanying drawing, in which the indicator is shown in Figure 1 inside elevation with a part of the housing removed and in Figure 2, inend elevation, partly in section.

In one end of a handle 1 made of plastic, wood or any other suitablenon-magnetic material is a housing comprising two brass plates 2 fixedto the handle and in which a circular disc 3 of permanent magnetmaterial is disposed. The disc is magnetised in a diametral direction.The two poles thus set up are marked N and S respectively on one side ofthe disc. The disc itself is so mount ed in the housing between thebrass plates on a pivot pressed or cast in a bore in the magnet that itcan readily turn about its own axis. As the point 5 of the instrument,which is formed by giving the aforesaid end an arrow head formationpointing in the direction of the longitudinal axis of the instrument,approaches the unknown pole of the magnet, the indication of the unknownpole appears in the window 4 in the brass housing.

The disc must be constructed of a permanent magnet material of highcoercivity. Preferably, it is made of sintered iron oxide and othermetallic oxides such as barium oxide, strontium oxide and [lead oxide.These so-called ferritic permanent magnet materials of sinteredpoly-oxides are of high coercivity in the region of 1800-2000 Oerstedand of low specific gravity. This property ensures high constancy of theinduced magnetic field as compared with extraneous fields. Consequently,the induced magnetisation direction is maintained with extremeexactitude, regardless of the strength of the magnetic fields whosepolarity is to be tested.

What I claim is:

1. A magnetic polarity indicator comprising a nonmagnetic housing, adiametrically magnetised disc made of an oxidic permanent magnetmaterial of high coercivity rotatably mounted in said housing, a windowin said housing, and an arrow head pointer extension of said housing,the position of said window in relation to the disc being determined sothat one of two polarity markings on the disc appear in said window whenthe poles of the disc align with the pointer.

2. A magnetic polarity indicator according to claim 1 comprising ahandle formed as a longitudinal extension of the housing in thedirection opposite to the pointer.

3. A magnetic polarity indicator according to claim 1, the pointer, thedisc axis and the window being one behind the other longitudinally ofthe indicator.

4. A magnetic polarity indicator according to claim 1, said disc beingmade of oxidic permanent magnet material consisting of iron oxide andnon-ferrous metal oxides.

5. A magnetic polarity indicator according to claim 4, said disc beingmade of iron oxide and at least one of the oxides selected from thegroup, barium oxide, strontium oxide and lead oxide.

References Cited in the file of this patent UNITED STATES PATENTS

